Bank check processing equipment is known which employs an ink jet printer for applying unique bar code markings to bank checks as they move through a high speed transport. The transport normally performs additional operations such as reading, microfilming, sorting, etc. The bar code printers have employed fluorescent inks to make the marking more distinct in the presence of other inks normally found on bank checks. Considerable interference still exists however since the fluorescent inks emit light in the visible spectrum and the other inks used to mark checks are selected for their ability to absorb visible light. Furthermore, other materials, whether inks or the paper itself, may produce visible fluorescence, especially under the stimulation of ultraviolet light. Thus conventional bank check marking inks can interfere with the readability of known fluorescent bar code marking, either by covering the marking or by adding extraneous fluorescence in addition to the marking. Interference by quenching of the fluorescence can exist even where the bar code is printed on top of a material that is absorptive of light in the wave-length of the bar code fluorescence.